1911] May-Flics of Fall Creek, N. Y. 113 



large erect tubercles on the occiput. Head, sub-quadrangular slightly 

 flattened with the head projecting forward; a triangular ridge with the 

 median ocellus at its apex projecting above the slightly indented fringed 

 frontal margin. (PL VI, fig. 2). Left maxilla figured on PL VIII, 

 fig. 3. Thorax, more than half the length of the trunk ; ci >lor dark above, 

 all except the prothorax pale below; prothorax, above slightly arched and 

 flaring at its postero-latera! angles, a tubercle at the middle of the lateral 

 margin and a smaller one on either side the middle of the posterior mar- 

 gin; mcsothorax with one median tubercle. Legs, with femora unevenly 

 brown above, pale below; tibiae brown with a pale transverse band 

 through the middle; tarsi brown with a pale transverse band at the 

 proximal end. Fore-femur (PL VII, fig. 5) shorter and thicker than the 

 others and with its anterior margin unevenly toothed. Anterior edges 

 of the other femora entire. Upper surfaces of all the femora with wart- 

 like elevations; posterior edge of the first femur and anterior and pos- 

 terior edge of the other femora with a row of sparse hairs. Abdomen 

 with gills present on segments 3-8, without Elytroid cover, superior 

 lamina entire; inferior lamina bifid fimbriate. Segments 2-7 with a 

 median double row of spines; posterior margins of segments 1-7 and 

 9-10 edged with short hairs; posterior margin of segment S with numer- 

 ous longer hairs. The posterior lateral angles of segments 3-10 pro- 

 duced backward into flat-pointed spines. Setae 3, with numerous hairs 

 on their outer and inner margins. 



Ephemerella rotunda, sp. nov. 

 (PI. VI, fig. 1; PI. VII, fig. 3; PI. VIII, fig. 5; PI. IX, fig. G.) 

 Occurrence, habitat. This species was taken in portion of 



Pleasant Brook, where there was little water and that strongly 



tainted by pipe drains. But four nymphs were captured. 



The two which were successfully reared proved to be females. 



The dates for their rearing were June 8 and 10. 



Measurements 

 Length of body Length of setae 



Female imago 10.5 m. m. 14 m. m. 



Female subimago 10 m. m. 10 m. m. 



Nymph 10.2 m. m. 6 m. m. 



Female imago. Thorax luteus; legs luteus or whitish; abdomen 

 brown; setae luteus with very distinct brown joinings. Head parch- 

 ment color. Thorax, above, luteus slightly darker on the mesothorax; 

 pleurae luteus to whitish with brown edges. Axillary cords (Snod- 

 grass, '09, The Thorax of Insects and the Articulations of the Wings, 

 p. 553) of the fore-wing prolonged into slender acute spines which pro- 

 ject backward on either side of the hinder lobe of the mesothorax. 

 Axillary cords of the hind wings prolonged in similar but less prominent 

 spines. Wings hyaline, costal region sub-hyaline (PL IV, fig. 6); 

 abdomen brown, pale at joinings and beneath. Color evidently mostly 

 due to contained ova. Sternite one longer than those following; ster- 



